Older, critically ill patients who survive their ICU stay frequently develop post-ICU syndrome (PICS) - a condition manifested by sarcopenia, weakness, malnutrition and neurocognitive decline - which occurs as a result of a critical illness, prolonged bed rest, catabolism, and polypharmacy. PICS frequently leads to chronic disability, prolonged mechanical ventilation (MV), functional deficits, and the need for extended rehabilitation in long term care facilities (LTCs). As the majority of patients admitted to ICUs ar = 65 years old, many of these patients are at high risk for PICS. Since the care of ICU patients is primarily focused on the medical management of the acute critical illness, there are limited resources and strategies available to prevent PICS. Evidence suggests mobility-based physical rehabilitation (MPR) combined with resistive training with neuromuscular electric stimulation (NMES) and high protein diets (HPRO) containing essential amino acids can mitigate the loss of muscle mass and function during bed rest in the elderly. We hypothesize that preventive therapy involving the addition of both NMES and HPRO to MPR early and throughout the ICU and hospital stay can mitigate PICS-associated sarcopenia, malnutrition, and immobility to confer valuable health benefits toward recovery. To test this, we will use a 2x2 factorial design in which older, MV ICU patients will all receive comprehensive ICU care and MPR, then be randomized to one of 4 groups: 1) MPR+NMES, 2) MPR+HPRO, 3) all 3 together, or 4) MPR alone (control), to determine independent and combined effects of the interventions. The Specific Aims are to 1) determine the effects of adding NMES and HPRO interventions to MPR on muscle mass, strength, and mobility function in older, critically ill MV patients while still inthe ICU, and 2) determine the effects of adding NMES and HPRO interventions to MPR on the clinical outcomes of time to weaning from MV, ICU/hospital length of stay and discharge disposition of these patients. This proposal capitalizes on the interdisciplinary collaboration among Pulmonary/Critical Care Intensivists, Physical Therapists, Geriatricians, Clinical Nutritionists, Statisticians and Nutrition and Metabolism clinical researchers examining the efficacy of our comprehensive rehabilitation approach. Our primary goal is to attenuate the severity of sarcopenia and functional decline in this older, critically ill population at risk for severe disability. Additionally, by focusing on maintaining skeletal muscle mass, function, and strength, we hope to improve clinical outcomes. The results of this pilot will provide preliminary data on feasibility, independent and combined effects of the interventions, and power estimates for an R01 proposal investigating the dose/intensity, and their effects on muscle biology, and physical and metabolic function that mediate the clinical outcomes. We posit this combined therapy will mitigate PICS-associated disability and speed the recovery from critical illness in older, MV ICU patients. This project has high overall impact as the intervention is easily administered by hospital staff and may greatly reduce the physiological and functional declines while hastening recovery during acute ICU hospitalization in older adults.